CO2 can be converted to useful fuels by electrochemistry method. As an effective strategy to address greenhouse effect and energy storage shortage, electrochemical reduction of CO2 still needs major improvements on its efficiency and reactivity. This work demonstrates a switchable pH-differential dual electrolyte microfluidic reactor (DEMR) that enhances the thermodynamic property and raises the electrochemical performance based on a laminar flow membrane-less architecture. It is the first time that the CO2 electrochemical reduction reaction is freed from the hindrances of thermodynamic limitation. DEMR has also achieved a high reactivity and Faradaic efficiency, revealing the potential for larger-scale applications in future urban energy network, such as a carbon-neutral energy conversion system.